Chapter 50. Deep sea Ostracoda, taxonomy, distribution and morphology

The Cylindroleberididae and Philomedidae, rich in species in littoral waters, are less important

in the deep-sea. The Rutidermatidae are represented only by a single species. Among the Philomedidae Igene is a true deep-sea genus.

Anteil der Unterordnungen an den

-Tiefseegattungen

TEXT-FIG.1-Diagram of the suborders of

the deep-sea genera

Anteil der Unterordnungen an den

TefseeaFten

TEXT-FIG.

2-Diagram of the suborders of

the deep-sea species.

The Halocypridina are more difficult to judge since their species are nearly completely pelagic

and many undertake vertical migrations thus occurring in water bodies of different depths. There

are no deep-sea taxa of genera or higher taxonomic level.

Among the Archiconchoeciinae Archiconchoecia contains 14 deep-sea species, and among the

Halocypridinae, Bathyconchoeciu, with 10 deep-sea species, has the majority of its species in this

environment. The entire family Thaumatocyprididae exists, though not exclusively, but with the

majority of its species in deeper waters. Danielopolina also occurs in marine caves.

The same is nearly true for the Cladocopina. The family Polycopidae, rich in species, populates

with many of its species the deep-sea bottom. In littoral biotopes this family lives in interstitial systems, both in the sublittoral and eulittoral regions. It is not possible to determine if this family

invaded the interstitial systems of the littoral zone from the deep sea or vice versa.

Species of Platycopa are also found in the deep sea, but the number of species here remains small.

The Podocopa present a confusing picture in that most families of this subclass have representatives in the deep sea. Sometimes it is difficult to decide if their occurrence is autochthonous or

if their shells have been transported to this biotope passively. In the tables, these species have been

marked “questionable”. Although this subclass is the richest in species, the number of exclusively

deep-sea taxa is also small.

701

T m

&DEEP-SEA

GENERA

AND NUMBER

OF THE SPECIES

OF MYODOCOPA-MYODOCOPIDA-MYODOCOPIN

A.

(“ma with exclusively deep-sea distribution are italicized)

ylF

i’

Cypridiniahe:

Tribes Cypridini:

Bathyvargula 2

Cypridina 2

Doloria 1

Haakcypridina I (only in deep-sea)

Macrocypridina 2

Metavargda 3

Paradoloria 2

Vargula 4

Dibes Azygozypridini (only in deep-sea):

Azygocypridina 8

Isocypridina I

Tribes Gigantocypridini (only in deep-sea) :

Gigantocypris 7

Family Cylindroleberididae (prevailing in littoral

regions) :

Subfamily Cylindroleberidinae:

Archasterope 1

Bathyleberis 2

Diasterope 1

Empoulsenia 2

Parasterope 3

Skogsbergiella 3

Synasterope 6

Subfamily Cyclasteropinae :

Cycloleberis 1

Asteropterygion 1

Family Philomedidae (prevailing in littoral regions) :

Subfamily Pseudophilomedinae:

Angulorostrum 2

Harbansus 1

Paramekodon 2

Subfamily Philomedinae :

Anarthron 1

lgene 2 (only in deep-sea)

Philomedes 11

Scleroconcha 3

Tetragonodon 2

Family Sarsiellidae:

Parasarsiella 1

Sarsiella 1

Spinacopia 7

Streptoleberis 1

Family Rutidermatidae (nearly exclusive to littoral regions):

Alternochelata 1

TABLE2-DEEP.SEA GENERA

AND NUMBER

OF SPECIES OF MYODOCOPA-HALOCYPRIDIDA-HALOCYPRIDINA

AND &ADOCOPIDA-CLADOCOPINA.

Family Halocyprididae:

Subfamily Archiconchoeciinae:

Archiconchoecia 14 (many in deep sea)

Subfamily Halocypridinae:

Bathyconchoecia 10 (many in deep sea)

Fellia 3

Halocypris 2

Subfamily Conchoeciinae :

Alacia 6

Boroecia 3

Conchoecetta 2

Conchoecia 20

Conchoecilla 3

Conchoecissa 5

Discoconchoecia 3

Gaussica 2

Loroecia 2

Metaconchoecia 8

Mikroconchoecia 4

Mollicia 5

Obtusoecia 1

Orthoconchoecia 4

Paraconchoecia 18

Paramollicia 5

Porroecia 1

Pseudoconchoecia 1

Spinoecia 2

Family Thaumatocyprididae (prevailing in deep sea) :

Danielopolina 1 (also found in caves!)

Thaumatoconcha 11

Thaumatocypris 1

Family Polycopidae:

Archipolycope 9 (many in deep sea)

Metapolycope 4

Polycope 29

Polycopsis 4

Pontopolycope 2

Pseudopolycope 2 (all in deep sea)

702 G. HARTMANN

AND G. HARTMANN-SCHRODER

Among the Bairdioidea, only the family Bythocyprididae is frequent at depth. Bythocypris contains 15 species in this environment, this being a large part of its species spectrum. Zabythocypris,

with 12 species known to date, exclusively inhabits the deep sea.

Very important for deep-sea ostracods is the genus Argilloecia of the Cypridoidea. The number

of its deep-sea species is constantly rising with the progress of deep-sea research. Seventeen species

have been found in the deep, and among ostracods sampled by the research vessels Polarstern

and Walther Herwig in Antartica, more have been found by the authors.

Among the Cytheroidea, generally rich in species, only occasionally have species been reported

from deeper waters. This is, for example, true for the families Leptocytheridae and Cytherideidae

which are very rich in littoral species. The Paradoxostomatidae, as forms which live mainly on

algae and suck their sap, are not inhabitants of lightless depths. There are some exceptions among

semi- and full-parasitic species. The Krithidae have, with the genus Krithe, a unit which includes

11, the Cytheruridae with Cytheropteron a unit with 16 deep-sea species. Most of the exclusivly

deep-sea inhabiting genera contain however, only a few species or are monotypic:

as well as the new genus Profmdocythere with 3 species recently noted by the present author

(1985).

Moreover, Table 3 shows that most of the remaining genera have at most 8, usually 1-5, deep

sea representatives.

Summing up, there is no doubt that many ostracod taxa inhabit the deep sea environment, but

it must also be pointed out that the number of exclusivelydeep-sea living taxa is astonishingly small.

btidermatidae

Anteil der Familien an den Tiefseearten der Mg(ocbapida

TEXT-FIG.

3-Diagram of the families of

the deep-sea species of Myodocopida.

QCytheridae

Q Leptocytheridae

0 Eucytheridae

0 Cytherideidae

6) Cytherettidae

@ Micmcytheridae

Anteil der Familien an den Tefseearten

der Cytheroidea

TEXT-FIG.

4. Diagram of the families of

the deep-sea species of Cytheroidea.

Deep-sea Ostracoda, Taxonomy, Distribution and Morphology 703

TABLE 3a-DEEP-sEA

GENERA

AND NUMBER

OF SPECIES OF PLATYCOPA AND POWCOPA.

Fmly Cytherellidae:

Cytherella 10

? Cytherelloidea 1 (uncertain)

Family Slpirridae:

Saipanetta 1

Family Bythocyprididae:

Bythocypris 15 (many in deep sea)

Orlovibairdia 1

Zabythocypris 12 fall in deep sea)

Superfamily Cypridoidea:

Family Macrocyprididae:

Macrocypris 8

Superfamily Bairdioidea:

Family Bairdiidae:

Subfamily Bairdiinae (prevailing in littoral regions) :

Bairdia 10

Bairdoppilata 4

Neonesidea 1

Paranesidea 3

Rerobairdia

Subfamily Pusselinae (prevailling in littoral regions) :

Anchistrocheles 2

Family Pontocyprididae:

ArgilIoecia 17 (many in deep sea)

Australoecia 3

Pontocypria 1

Pontocypris 6

hopontocypris 1

Family Candodidae (prevailing in littoral regions) :

? Aglaiocypris 1 (uncertain)

? Paracypris 2 (uncertain)

DISTRIBUTION

OF DEEP-SEA

OSTRACODA

Because of the great spatial, wide geographical, temporal and ecological continuity of the deepsea environment, zoogeographers agree that many, if not most, deep-sea animal species have a wide

distribution. Is this also true of deepsea ostracods?

Analyzing the distribution of the 520 deep-sea species and subspecies it is not possible to confirm

this general statement as applying to ostracods. On the contrary, most of the species appear to have

only small vertical and horizontal ranges! This is possibly due to the lack of knowledge of deep-sea

ostracods. However to postulate a wide distribution of deep-sea ostracods simply because this is

true for other animal groups is not permissible.

Among the Myodocopina species of the checklist, only two species are found to be widely or

circumtropically distributed. All others have a small range.

The pelagic Halocypridina naturally have a wider distribution. Twenty-three of the deep sea

species have a circumtropical distribution, while 15 occur worldwide. However, the wide geographical distribution is mostly combined with a wide vertical distribution, that is, 18 of the 23 circumtropical species are also found in epipelagic communities, with the same being true for 12 of the

18 worldwide species.

Not a single species of the Cladocopina is recorded as having a wide distribution!

The Platycopa appear to be widely distributed with several species having been recorded from

widely separate localities. It is however remarkable that only these three species appear to have a

wide range, which clearly do not represent a single species. The Bairdioidea of the Podocopa show

a similar picture. A wide distribution is also reported for species described by Brady (1880). The

systematic status of these species, however, is not clear.

Among the Cytheroidea the following species are evidently widely distributed:

Description.-Carapace large, alate, broadly elliptical in side view with the greatest height at

about mid-length. Dorsal margin of left valve evenly rounded, dorsal margin in right valve straight,

Surface appears smooth under ordinary optical examination; the SEM shows it to be finely

pitted with incipient reticulation, but smooth where it approaches the alar rim. Alar rim smooth with

four fine, anastomosing, longitudinal ribs on its ventral surface. Short blunt caudal process. A

flange is present anteriorly, ventrally and posteriorly where it ends in a small posteroventral point

(Pl. 1, fig. 4). The posterior part of this flange is apparent in lateral view (Pl. 1, figs. 1,3) Hinge antimerodont in the right valve with five, well-developed teeth anteriorly and six or seven posteriorly,

joined by a finely locellate groove of uniform width which may even become a little constricted at

its extremities. Left valve complementary with straight accommodation groove to receive the